A company is testing a web application that runs on Amazon EC2 instances behind an Application Load Balancer. The instances run in an Auto Scaling group across multiple Availability Zones. The company uses a blue/green deployment process with immutable instances when deploying new software. During testing, users are being automatically logged out of the application at random times. Testers also report that, when a new version of the application is deployed, all users are logged out. The Development team needs a solution to ensure users remain logged in across scaling events and application deployments. What is the MOST efficient way to ensure users remain logged in?

A. Enable smart sessions on the load balancer and modify the application to check for an existing session.
B. Enable session sharing on the load balancer and modify the application to read from the session store.
C. Store user session information in an Amazon S3 bucket and modify the application to read session information from the bucket.
D. Modify the application to store user session information in an Amazon ElastiCache cluster.